Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

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Re: hearing the big picture?

Posted by tomservo (M) on June 19, 2006 at 05:45:40

In Reply to: Re: hearing the big picture? posted by Tom Dawson on June 18, 2006 at 21:41:56:

Hi Tom

You said “There are few if any mics that make it to the recording studio having less than 100db S/N ratio. 120db or better is more typical.”

I have to say you have my curiosity peaked, please what recording mic’s have 100dB or 120dB or better S/N ratio? I have a B&K 4007 and a pair of Earthworks M-55’s which all fall short of this.

You said “Lots of what you 'hear' on a CD is in the lowest 48 db, in fact, probably most of it, considering all the spatial, frequency, timing and interchannel information necessary to make a reasonable facsimile of a recording of music. Not to say that most commercially purveyed digital is not deficient in these regards.”
If there were a “lot” of info far down from the peak levels, how were many fine recordings made on open reel tape which had FAR less (like half or less) dynamic range?
While I didn’t measure every CD made, I did measure many and also some like Flynn and the BB’s thought to be demo quality. With the exception of the silent parts between songs, there wasn’t anything like the possible dynamic range in the recordings.

Conversely, lets pretend you are a typical listener, you have speakers with 90dB 1W 1M sensitivity and a 100W amp. This (if you’re listening only a meter away and have no power compression etc) could only reach a Peak SPL of 110 dB SPL Assuming a normal quiet residence, the noise floor could be 20 to 40dB.
This means, if your willing to sit a meter from the speakers, that you could “hear” a possible 70 - 90dB of dynamic range.
If you choose to sit further away or listen at a lower average sound level (because the average level is –10 to –20 usually from peaks) , then the range is even less.

24/96 is generally considered faultless via listening but higher rates and bit counts are used for reasons I mentioned.
One can see why it is a good idea to stay in the “top half” when one considers half of the total data bits describe the top 6dB of output. Each time the level is reduced 6dB (Voltage cut in half) the resolution is also cut in half. Only one bit describes the bottom 6dB of range. High bit counts make setting the exact level RE:0dB much less critical.
Best,

Tom

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